This application claims the benefit of German Application DE P 10020665.4 filed Apr. 27, 2000, herein incorporated by reference.
The present invention relates to a method of operating a textile machine having plural workstations at each of which a yarn is unwound from supply bobbins, checked, cleaned of yarn defects, especially by a splicing or other yarn joining procedure, and then rewound into larger-volume cheeses.
As is known, yarn produced on a textile machine at the outset of the overall yarn production process, preferably a ring spinning machine, is wound onto relatively small-volume spinning cops. Thus, to prepare the yarn for use in subsequent machinery and operations, the yarn is rewound onto considerably larger package carriers, typically so-called cheeses. During this rewinding process, the yarn is constantly checked for any yarn defects, e.g., by a yarn cleaner or a slub catcher, as is explained in detail, e.g., in German Patent Publication DE 196 40 184 A1. Detected yarn defects are immediately removed.
More specifically, when the yarn cleaner discovers a yarn defect, a controlled yarn cut takes place immediately by means of a yarn separating device arranged in the area of the yarn cleaner. The lower yarn length leading from the spinning cop thereby produced is fixed in a yarn tensioner and held in a position ready for a subsequent yarn joining procedure while the upper yarn length trailing from the cheese and containing the yarn defect, is initially wound onto the cheese. The cheese is lifted off of its associated drive drum at the same time as the cutting of the yarn and is braked to a standstill by an appropriate bobbin brake. The upper yarn length wound onto the surface of the cheese is aspirated by a suction nozzle. In particular, the mouth of the suction nozzle is positioned in the area of the cheese surface and the cheese is slowly rotated in a reverse direction to unwind its yarn. After the defective yarn length has been removed, the upper yarn is re-joined to the lower yarn in a splicing device into which the lower yarn had previously been inserted by a gripper tube.
Even though the yarn splice produced thereby represents a joining that is nearly uniform with the yarn and is hardly visible in a subsequent fabric, cheeses in which a predetermined number of such yarn splices is exceeded are often considered as inferior or lower-grade cheeses by subsequent processing operations, e.g., weaving mills, and the production of such cheeses should therefore be avoided, if possible.
European Patent Document EP 0 628 509 B1 teaches a bobbin winding machine in which the traveling yarn is continuously checked, as is customary, by a yarn cleaner for yarn defects. In addition, the yarn length drawn off from the spinning cop is continuously detected in this known device. If the number of the detected yarn defects relative to a certain amount of the yarn to be rewound exceeds an adjustable number, the winding process is stopped and the yarn is cut. A predeterminable amount of yarn is subsequently drawn off from the presented spinning cop and removed by a special suction removal device. In other words, this known method is based upon the fact that only a relatively limited, defective amount of yarn is present on a spinning cop which amount is removed by the suction removal action described above. The lower yarn leading from the spinning cop is subsequently re-joined, as is customary, in an appropriate splicing device to the upper yarn retrieved from the cheese and the rewinding process continued.
However, this known method has the serious disadvantage that spinning cops also often have defective yarn material throughout, so that defective yarn continues to be wound on even after the suction removal action. In addition, this known method has the disadvantage that the yarn amount that has been cleaned out but still has disproportionately many yarn joinders remains in every instance on the cheese.
In view of the above-described state of the art, it is an object of the present invention to develop a method that assures than only cheeses are manufactured in which the number of yarn joinders per associated reference yarn length does not exceed an adjustable number.
The invention addresses this objective by providing an improved method of operating a textile machine of the type having plural workstations at each of which a yarn is unwound from supply bobbins, checked, cleaned of yarn defects and then rewound into larger-volume cheeses. More specifically, the present method basically comprises the steps of registering yarn joinders performed during the winding process and, when a predetermined number of yarn joinders are exceeded over a predetermined reference yarn length, stopping the winding process and unwinding and removing the reference yarn length having the excessive number of yarn joinders from the cheese.
The method in accordance with the invention has the particular advantage of constantly assuring that the cheeses produced have only a certain, adjustable, tolerable number of yarn joinders. That is, the method of the invention assures that the cheeses always have a certain minimum quality level, at least as concerns the number of their yarn joinders.
A preferred embodiment provides that the yarn length wound onto the cheese as well as the number of yarn joining procedures that occurred are monitored by the workstation computer of the particular workstation. Thus, the workstation computer, that is already present at each workstation m any case, is reprogrammed by software so that it can assume additional functions.
According to another aspect of the present invention, the number of joining procedures acceptable in a certain yarn length and the particular reference yarn length can be adjusted in a central control unit of the textile machine. Since this central control unit communicates with all workstation computers, it is possible to change and/or correct the number of tolerable joining procedures as well as the associated reference yarn length in a simple and rapid manner, e.g., by downloading the particular adjustment data.
However, it is basically also possible to input the particular adjustment data directly into the individual workstation computers. Such a method can be suitable, for example, if several batches with differing quality requirements for the cheeses are processed simultaneously on a bobbin winding machine.
A further embodiment of the invention advantageously provides that the reference yarn length recognized as defective is removed, if necessary, by the suction nozzle of the particular workstation. In this instance, existing hardware is also used almost without further expense for this additional purpose.
Further details of the invention can be understood from an exemplary embodiment described in the following disclosure with reference to the accompanying drawings.